Applied Catalysis A, General (v.514, #C)

Contents (iii-x).

Effect of K and Bi doping on the M1 phase in MoVTeNbO catalysts for ethane oxidative conversion to ethylene by E.V. Ishchenko; T.Yu. Kardash; R.V. Gulyaev; A.V. Ishchenko; V.I. Sobolev; V.M. Bondareva (1-13).
Display OmittedThe effect of potassium and bismuth doping on the morphology and structure of M1 phase, which determines the activity of MoVTeNbO catalysts in the oxidative conversion of ethane to ethylene, was studied. According to XRD, HRTEM and XPS data, the introduced K and Bi enter the M1 phase and do not form individual compounds. The addition of potassium is accompanied by anisotropic growth of the M1 phase particles: an increase in potassium content enhances the growth of particles along the [0 0 1] direction. The insertion of bismuth does not change the morphology of M1 phase but produces structural features (extended defects, disorientation of the crystal structure) that increase the fraction of accessible surface formed by {0 0 1} faces. Along with the structural and morphological transformations, the both additives affect the ratio of V5+/V4+ and Mo6+/Mo5+ cations and the enrichment of the catalyst surface with tellurium. The observed changes in physicochemical characteristics of the promoted catalysts correlate with changes in the catalytic properties.
Keywords: Ethane oxidative dehydrogenation; M1 phase; Doping; Bi; K;

Ternary copper–cobalt–cerium catalyst for the production of ethanol and higher alcohols through CO hydrogenation by Peng Wang; Junfeng Zhang; Yunxing Bai; He Xiao; Shaopeng Tian; Hongjuan Xie; Guohui Yang; Noritatsu Tsubaki; Yizhuo Han; Yisheng Tan (14-23).
Display OmittedA series of highly dispersed carbon nanotube (CNT)-supported copper–cobalt–cerium catalysts were prepared using a facile and effective co-impregnation method. The catalysts were then examined for their ability to selectively convert syngas into ethanol and higher (C2+) alcohols with a narrow range distribution. Superior selectivity values of 31.6% and 60.2% for the formation of ethanol and C2+ alcohols, respectively, were achieved over the CuCoCe/CNTs catalyst. These values were considerably higher than those achieved over a Cu–Co bimetallic catalyst (i.e., 16.6% and 29.7%). The addition of ceria alters the electronic and geometric interactions with the cobalt species, thereby promoting the reduction of CoO and the formation of a Co–CeO2− x interface as a new active site for enhancing CO dissociation and terminating carbon chain growth by oxygenation. In contrast, the CNTs serve as reactors to ensure intimate contact among the metal particles at the nanoscale. The structure–performance correlation studies suggest that the formation of the Co–CeO2−x interface plays a key role in determining the distribution of short-chain alcohols.
Keywords: CO hydrogenation; Higher alcohol synthesis; CuCoCe; Carbon nanotube;

γ-MnO2 displayed the best NO catalytic oxidation activity, especially in the low temperature range. The large specific surface area and pore volume of the γ-MnO2 were supposed to have beneficial effect, besides, the active oxygen in the γ-MnO2 resulted from the random structure of γ-MnO2 was also responsible for the superior activity.Display OmittedThe NO catalytic oxidation activities of single-phase α-, β-, γ-, and δ-MnO2 were investigated. All the catalysts were systematically characterized using various techniques. The results showed that the catalytic activities were significantly affected by the MnO2 phase structures. Among the four catalysts, the urchin-like γ-MnO2 showed the best NO catalytic oxidation activity across the studied temperature range, with the largest NO conversion, namely 88%, at 280 °C. This is good activity, even compared with those of noble-metal-based catalysts. It also displayed the best activity during long reaction times. The NO catalytic oxidation activities of the other three catalysts decreased in the order α- > β- > δ-MnO2. The various phase structures of MnO2 contain the same [MnO6] octahedral units, but with different linking modes. γ-MnO2 has a disordered structure, resulting in larger numbers of active oxygen species, leading to a better catalytic performance.
Keywords: Single-phase MnO2; NO catalytic oxidation; Tunnel structure; Morphology; Activated oxygen;

Display OmittedTwo high-activity supported-Pd catalysts (Pd/V2O5/TiO2/SBA-15 and Pd/V2O5/TiO2/MCM-41) for selective catalytic reduction of NO with H2 were studied. They differ only by the mesoporous-silica support: SBA-15 vs. MCM-41. Although the SBA-15 supported catalyst had a lower surface area, it showed a higher NO conversion (95% vs. 84%, at a high space velocity of 4.6 × 104 1/h). Two pieces of direct and related evidence are shown for the role of hydrogen spillover in enhancing the catalytic activities of these two catalysts. A comparison of hydrogen adsorption isotherms (via the Benson-Boudart method) show more spillover on the SBA-15 supported catalyst. The results from the transient kinetics experiments also showed that the amount of spiltover hydrogen stored on the Pd/V2O5/TiO2/SBA-15 under dynamic reaction conditions was significantly higher than that on Pd/V2O5/TiO2/MCM-41 (7.3 μmol/g vs. 2.1 μmol/g). Catalytic performance of the two catalysts for practical applications is reported. The favorable effect of hydrogen spillover on H2-SCR could be used as a new strategy for improving the performance of noble-metal H2-SCR catalysts.
Keywords: Selective catalytic reduction; H2-SCR; Pd-based catalysts; Hydrogen spillover; Nitric oxide reduction;

A novel reusable polymer nanoparticles grafted hydroxyl-functionalized phosphonium-based ionic liquid (PNPs-HPIL) was first prepared, and evaluated as efficient for the synthesis of cyclic carbonates from CO2 and epoxides. The as-fabricated PNPs-HPIL catalysts exhibit good catalytic acitivity, stability, and reusability, which are benefical to practical application in industry.Display OmittedA promising new strategy for fabricating polymer nanoparticles that are grafted with hydroxyl-functionalized phosphonium-based ionic liquid (PNPs-HPIL) through copolymerization of EGDMA and HPIL was established. The PNPs-HPIL catalyst exhibits good catalytic activity for the synthesis of cyclic carbonates through cycloaddition of CO2 to epoxides. At a catalyst loading as low as 0.47 mmol%, the PC yield is above 96.0% and PC selectivity almost 100%. It is noted that the hydroxyl groups of PNPs-HPIL play an important role for facilitating the cycloaddition reaction through the hydrogen bonding between hydroxyl groups and epoxides. Furthermore, the PNPs-HPIL catalyst shows good stability and reusability, which are beneficial to practical application in industry.
Keywords: Polymer nanoparticles; Phosphonium-based ionic liquid; CO2; Epoxide; Cyclic carbonate;

Methanol synthesis from CO2 and H2 over Pd/ZnO/Al2O3: Catalyst structure dependence of methanol selectivity by Jinghua Xu; Xiong Su; Xiaoyan Liu; Xiaoli Pan; Guangxian Pei; Yanqiang Huang; Xiaodong Wang; Tao Zhang; Haoran Geng (51-59).
Display OmittedCO2 hydrogenation to methanol was investigated over Pd/ZnO/Al2O3, focusing on the influence of the preparation method, reduction temperature and Pd loading on the catalytic performance. The structure of each catalyst was thoroughly examined using various techniques. The results indicated that the methanol selectivity depended on the content of PdZn alloy, which changed dynamically with varying the preparation methods and pretreatment procedures of the catalysts. More specifically, the ratio of PdZn/Pd0 in the bimetallic compound increased with the rise of the reduction temperature, which eventually led to the increase of methanol selectivity. Additionally, the EXAFS results revealed the presence of ZnO x modified Pd species when the Pd loading was decreased to be lower than 2 wt%. However, the CH3OH selectivity remained almost identical when the reactions were conducted under similar CO2 conversions. Therefore, we conclude that both the PdZn alloy and Pd modified by ZnO x islands are the active sites for methanol synthesis from CO2 hydrogenation.
Keywords: CO2 hydrogenation; Methanol synthesis; Supported Pd catalyst; PdZn alloy;

Visible-light photocatalytic activity of chitosan/polyaniline/CdS nanocomposite: Kinetic studies and artificial neural network modeling by M.H. Rasoulifard; M.S. Seyed Dorraji; A.R. Amani-Ghadim; N. Keshavarz-babaeinezhad (60-70).
Display OmittedChitosan/polyaniline (CS/PAni), chitosan/CdS (CS/CdS) and chitosan/polyaniline/CdS nanocomposite were synthesized and characterized using X-ray diffraction pattern analysis, FT-IR spectroscopy and scanning electronic microscopy. The adsorption performance and photocatalytic activity of CS/PAni/CdS was compared with CS/PAni and CS/CdS in the removal of Reactive Blue 19 (RB19) dye. After five cycles of experiments under visible light irradiation, CS/PAni/CdS retained high photocatalytic activity which confirmed good stability of nanocomposite. Moreover, the kinetics of decolorization was investigated and novel equation rate for dye removal was established by considering two parallel mechanisms including adsorption and surface photocatalytic degradation of dye by CS/PAni/CdS. Artificial neural network was employed to develop a model for predicting the decolorization efficiency and determining the relative importance of operational parameters. A 3-layer perceptron network with optimized 5:10:1 topology could provide adequate predictive performance (R 2  = 0.983). Moreover, the photocatalytic degradation of RB19 was monitored by measuring the total organic carbon (TOC) and GC–MS analysis, enabling the evaluating the mineralization and identifying the intermediates. During 120 min of experiment, more than 80% of TOC was removed.
Keywords: Photocatalyst; Nanocomposite; Kinetics; Artificial neural networks; Product identification;

Cross-coupling of p-xylene to 2,2′,5,5′-tetramethyl 1,1′-biphenyl on supported vanadia catalysts by Gheorghiţa Mitran; Octavian Dumitru Pavel; Mihaela Florea; Vasile I. Pârvulescu (71-82).
Display OmittedAluminas with different textural characteristics were synthesized by carbonate, citrate and urea sol–gel methods. All supports were impregnated with an aqueous solution of ammonium metavanadate in order to obtain the same loading of vanadia (7% wt V2O5), and then characterized by XRD, N2 physisorption, Raman spectroscopy and NH3-TPD. In this way it was possible to tune the characteristics of the supported vanadia as it has also been demonstrated from the catalytic behavior of these materials in the cross-coupling of p-xylene to 2,2′,5,5′-tetramethyl 1,1′ biphenyl (biaryl) in the presence of O2. Alumina prepared via the carbonate method and calcined at 500 °C proved to be the most suitable support affording, for a level of conversion of 8%, selectivities to biaryl of 96%. It corresponded to an enough high dispersion of vanadium to allow the cleavage of the C―H bonds. Recycling experiments confirmed the stability of these catalysts.
Keywords: Alumina supported vanadia nanoparticles; p-Xylene cross coupling; Biaryl synthesis;

Display OmittedIGCC-CCS process is one application of a cobalt-molybdenum (Co–Mo)-based water-gas shift catalyst (sour shift catalyst). In this process, it is necessary for the shift reaction to progress efficiently with a small amount of steam in order to suppress CO2 emissions and to increase production efficiency. However, if the amount of steam used in the shift reaction is decreased, there is a possibility that the selectivity of side reactions represented by hydrocarbon production and carbon deposition increases. Therefore, we investigated the effects of various operating parameters regarding the selectivity and reaction mechanism of the side reactions with a reduced steam supply in the shift reaction for Co–Mo-based shift catalyst. Among the side reactions accompanying the shift reaction, the reaction of hydrocarbon production progresses due to the Fischer–Tropsch reaction and increases at a high temperature, high pressure, low steam supply, and long residence time. Moreover, the reaction of carbon deposition in the catalyst progresses due to the Boudouard reaction, which produces carbon directly from the CO source and the deposition increases at a low temperature, high pressure, and low steam supply. Furthermore, the selectivity of the shift reaction of the Co–Mo-based catalyst is high in the co-existing steam conditions, and the shift reaction progresses even if there is a small amount of steam in the reaction gas.
Keywords: Selectivity; Shift reaction; Fischer–Tropsch reaction; ASF plot; Boudouard reaction; Hydrocarbon production; Carbon deposition;

The effect of catalyst pellet size on nickel carbonyl-induced particle sintering under low temperature CO methanation by J. Barrientos; N. González; M. Lualdi; M. Boutonnet; S. Järås (91-102).
Display OmittedThe present work aims to evaluate the effect of catalyst pellet size on deactivation due to nickel carbonyl-induced particle sintering. For that purpose, a γ-Al2O3-supported nickel catalyst was prepared and tested under low temperature and high CO partial pressure. A total of four different pellet sizes were employed in the present study. It was found that the deactivation rate decreases with increasing pellet size. A very severe deactivation was observed when using small pellets. Large pellets exhibited instead a more stable performance. This difference in catalyst stability was explained by X-ray diffraction analyses which revealed that the growth of the nickel particles was very severe when using small pellets. An evaluation of heat and mass transfer phenomena in these four pellets was also conducted. It was found that, under the present low temperature reaction conditions, the temperature at the catalyst external surface can greatly differ from that in the bulk gas when using sufficiently large pellets. It was also shown that, for large pellets, the major part of the interior of the catalyst is exposed to negligible CO partial pressures and high temperatures, fact that can reduce the potential for nickel carbonyl formation.
Keywords: Methanation; Deactivation; Nickel carbonyl; Sintering; Heat and mass transfer; Alumina;

Effect of sulfur on α-Al2O3-supported iron catalyst for Fischer–Tropsch synthesis by Jing-Dong Xu; Ze-Ying Chang; Kong-Tao Zhu; Xue-Fei Weng; Wei-Zheng Weng; Yan-Ping Zheng; Chuan-Jing Huang; Hui-Lin Wan (103-113).
Incorporation of sulfur into a Fe/α-Al2O3 catalyst decreased the CO conversion, the C5+ selectivities as well as the O/P ratio of the C2–C4 products and promoted the formation of C2–C4 hydrocarbons.Display OmittedThe effects of sulfur modification (S/Fe = 0.001 ∼ 0.05, molar ratio) on the α-Al2O3-supported iron catalysts for the Fischer–Tropsch synthesis (FTS) were investigated. It was found that the presence of sulfur promoted the reduction of FeO to metallic Fe during the H2 reduction process, but decreased the rates of reduction, carburization and carbon deposition of the catalysts when CO is used as the reducing agent. Both the sulfide (S2−) and sulfate species ( S O 4 2- ) are found in the SxFe/α-Al2O3 catalysts after H2 reduction and FTS reaction. The sulfide species in the H2-reduced SxFe/α-Al2O3 catalysts are located on the surface of metallic Fe particles. The intensity of H2 desorption peak around 500 K is enhanced by a small amount of sulfur, while an excess of sulfur suppresses the H2 adsorption. The dissociative adsorption of CO on H2-reduced catalysts was also found to be inhibited by the presence of sulfur. The activity of the Fe/α-Al2O3 catalyst can be decreased significantly by the addition of sulfur due to the inhibition of CO dissociation and thus reduce the formation of iron carbide phases under FTS reaction conditions. Resistance to sulfur poisoning of the Fe/α-Al2O3 catalyst was found to improve with increasing the reaction temperature. The presence of sulfur also suppressed the formation of C5+ hydrocarbons and shifted the products to C2–C4 hydrocarbons. At the same time, the olefin to paraffin (O/P) ratio of the C2–C4 hydrocarbons decreased with increasing S/Fe molar ratio. These may have resulted from the increasing of the H/C ratio on the surface of sulfur modified catalyst under FTS conditions.
Keywords: Fischer–Tropsch synthesis; Iron; Sulfur; α-Al2O3; Lower olefins;

Effect of nitric oxide on the formation of cobalt–aluminum oxide structure from layered double hydroxide and its further transformation during reductive activation by Alexander A. Khassin; Irina I. Simentsova; Alexander N. Shmakov; Natalia V. Shtertser; Olga A. Bulavchenko; Svetlana V. Cherepanova (114-125).
Display OmittedThe presence of nitric oxide NO in the gas phase was shown to decrease the decomposition rate of the hydrotalcite-like Co–Al LDH phase in the catalysts prepared by co-precipitation or deposition on Al2O3 under the condition of urea hydrolysis. The decrease in LDH decomposition rate is related to the formation of a more crystallized phase of the spinel-like Co–Al oxide due to the ability of nitric oxide to transfer oxygen in consecutive reactions of the oxidation to NO2 and reduction to NO. The difference in the coherent scattering domain size of the catalyst samples precalcined in the presence of NO or in a pure inert gas is retained at all consecutive steps of the reductive heat treatment in hydrogen: after the formation of a cubic phase of the (Co, Al)O oxide and its reduction to metallic cobalt. The observed changes in the degree of crystallinity and dispersion of the active metal exert only a slight effect or even no effect on the activity of the catalysts in Fischer–Tropsch synthesis. Noteworthy are a lower selectivity for methane and a greater fraction of olefins in the products obtained on the catalysts precalcined in a flow of inert gas containing 3% NO.
Keywords: Cobalt; Layered double hydroxide; Nitric oxide; Fischer–Tropsch synthesis;

1,5-Dinitronaphthalene hydrogenation to 1,5-diaminonaphthalene over carbon nanotube supported non-noble metal catalysts under mild conditions by Wei Xiong; Kai-Jun Wang; Xi-Wang Liu; Fang Hao; Han-Yan Xiao; Ping-Le Liu; He-An Luo (126-134).
Display OmittedCarbon nanotubes (CNTs) were firstly thermal treated and then acid treated in HNO3 or mixture of HNO3 and H2SO4. The treated carbon nanotubes were used as support to load nickel to prepare non-noble metal hydrogenation catalysts. These catalysts were characterized and applied in 1,5-dinitronaphthalene hydrogenation. The characterization results indicate that acid modified carbon nanotubes not only possess a more hydrophilic surface by introducing a variety of oxygen-containing functional groups, but also improve the nickel dispersion, hydrogen uptake quantity and metallic surface area. The Ni/CNTs catalysts show good catalytic activity in 1,5-dinitronaphthalene hydrogenation under mild reaction conditions, and the Ni/CNTs-4 gives the best result of 100% conversion of 1,5-dinitronaphthalene and 92.04% selectivity to 1,5-diaminonaphthalene under 0.6 MPa and 393 K. The influences of reaction conditions and metal loading amount are discussed, and a possible reaction routes of 1,5-dinitronaphthalene hydrogenation is proposed. Such non-noble metal hydrogenation catalysts are expected to replace the present supported palladium or platinum noble catalysts in industry.
Keywords: 1,5-Dinitronaphthalene; 1,5-Diaminonaphthalene; Hydrogenation; Carbon nanotubes; Non-noble metal catalysts;

Dehydrogenation properties of ZnO and the impact of gold nanoparticles on the process by Patrycja Suchorska-Woźniak; Olga Rac; Roman Klimkiewicz; Marta Fiedot; Helena Teterycz (135-145).
Display OmittedThe article presents the results of catalytic and surface properties of pure zinc oxide synthesized by hydrothermal method and surface-doped with gold nanoparticles. As a test reaction, the catalytic transformation of n-butyl alcohol towards the dehydrogenation or bimolecular condensation of symmetric ketone or an ester was studied. The tested materials catalyse both consecutive reactions, wherein the transformation towards the ketone is dependent on the presence of surface oxygen vacancies, whose concentration depends on the temperature. In turn, the transformation to the ester occurs in the presence of gold nanoparticles deposited on the surface of zinc oxide. The difference in work function of electrons from these materials create a change in the electron concentration in the surface area and will shift the balance of the coupling reaction of hydrogen with lattice oxygen, which prefers the formation of aldehyde and ester. The results were compared with the catalytic properties of other previously studied oxide systems in this group of changes. This analysis enabled the development of the mechanism of transformation and explanation of the impact of gold on the kinetics of the process.
Keywords: Catalysis; Dehydrogenation; Gold nanoparticles; Zinc oxide;

Continuously enhanced photoactivity of hierarchical β-Bi2O3/Bi2S3 heterostructure derived from novel BiO2CH3 octagonal nanoplates by Yangyang Zhang; Yiping Guo; Bijun Fang; Yujie Chen; Huanan Duan; Hua Li; Hezhou Liu (146-153).
Display OmittedBiO2CH3 nanoplate, a new organometallic crystal, with octagonal morphology is successfully prepared using methanol solvothermal method and further employed as template to fabricate porous β-Bi2O3 octagonal nanoplates with a thickness of less than 50 nm. Then a series of hierarchical octagonal haystack-like β-Bi2O3/Bi2S3 hybrids with large heterointerface and small bandgaps (1.36–1.44 eV) are constructed. It is found that, different from many regular photocatalysts that suffer from shrink of photocatalytic efficiency, the photoactivities of all β-Bi2O3/Bi2S3 heterostructures are continuously enhanced with growing test cycles, owing to the formation of Bi2O3−x S x solid solution, in which the built-in electric filed induced by lattice distortion can brings about higher e/h+ separation efficiency. The gradually increasing photocatalytic activity can reach to an up limit in about 5 photocatalytic cycles and maintain at this level. β-Bi2O3/Bi2S3 heterostructure loaded with 20 mol% of Bi2S3 is demonstrated to be the best photocatalyst and capable of fully decomposing Rh B in 30 min. Our work provides deep insights into the nature of the inversed photocatalytic behavior and facilitates the advanced design of photocatalysts with unabated photoactivities.
Keywords: Organometal; Heterostructure; Nanoplates; Photoactivity; Solid solution;

Catalysis of metal supported zeolites for dealkylation–transalkylation of alkyl-aromatics by Sulaiman S. Al-Khattaf; Syed A. Ali; Abdullah M. Aitani; Khalid J. Al-Nawad; Chih-Hsuan Chiu; Tseng Chang Tsai (154-163).
Display OmittedIn search for catalysts with tailorable pore structure for simultaneous dealkylation and transalkylation of C9 aromatics to produce xylenes, the catalytic performance of layered MWW-type zeolites were compared with mordenite (MOR) in terms of the effects of zeolite topology, metal(s) incorporation and preparation method. During the catalytic reaction of trimethylbenzene (TMB)–methylethylbenzene (MEB) model feed, the ion exchanged Pt-MOR catalyzed a significantly higher MEB dealkylation than H-MOR resulting in an increase in xylene yield (from about 27 wt% to 34 wt%). Impregnation of Re into the Pt exchanged zeolite would moderate Pt hydrogenation activity and reduce MEB conversion. Compared to MOR, MCM-22 and ITQ-2 exhibited lower xylene yield and higher selectivity of C10 aromatics. On the other hand, pillared MCM-36 catalyzed escalated TMB conversion and higher xylene yield at the expense of product selectivity of toluene and C10 aromatics. The improvement in the catalytic performance of MCM-36 is attributed to the enlarged supercage for favorable catalysis for toluene-TMB transalkylation than TMB disproportionation.
Keywords: Dealkylation; Transalkylation; MWW zeolites; Platinum; Rhenium; Xylenes;

Effect of in-situ sulfur poisoning on zinc-containing spinel-supported cobalt CO hydrogenation catalyst by Zhenxin Liu; Depeng Wu; Yu Xing; Xuehui Guo; Shaoming Fang (164-172).
Display OmittedThe concentration of S in feedstock has significant effect on catalytic activity. The rate of S sorption by Co/ZnAl2O4·Al2O3 catalyst at 100 ppmv S is 3.1 times higher than that by Co/γ-Al2O3 catalyst, making the former a potential catalyst (or sorbent) to be loaded at the top portion (or pre-catalytic bed) of a fixed-bed FT reactor to scavenge sulfur from syngas feedstock.Literature about sulfur addition over AB2O4 spinel-supported cobalt CO hydrogenation catalysts is sparse. Research about the use of carbon disulfide as the sulfur carrier for the poisoning of cobalt catalysts is also sparse. In this study, effect of the addition of 0.1–1, 10, 100 and 300 ppmv of sulfur (injected as carbon disulfide) on the structure and performance of a Co/ZnAl2O4·Al2O3 CO hydrogenation catalyst was characterized (by ICP, XRD, nitrogen sorption and FESEM) and evaluated in a fixed-bed reactor. The addition of 0.1–1 ppmv of sulfur did not have a significant negative effect on the activity of Co/ZnAl2O4·Al2O3 catalyst. At S equivalent concentration of 100 ppmv, the deactivation of Co/ZnAl2O4·Al2O3 catalyst was reversible to some extent. At identical S equivalent concentration of 100 ppmv, the rate of S sorption by Co/ZnAl2O4·Al2O3 catalyst was 3.1 times higher than that by Co/γ-Al2O3 catalyst, making the former a potential catalyst (or sorbent) to be loaded at the top portion (or pre-catalytic bed) of a fixed-bed FT reactor to scavenge sulfur from syngas feedstock.
Keywords: CO hydrogenation; Cobalt catalyst; Sulfur poisoning; Deactivation; Fischer-Tropsch synthesis;

On the thermal stabilization of carbon-supported SiO2 catalysts by phosphorus: Evaluation in the oxidative dehydrogenation of ethylbenzene to styrene and a comparison with relevant catalysts by Valeriya Zarubina; Hesamoddin Talebi; Harrie Jansma; Kinga Góra-Marek; Christian Nederlof; Freek Kapteijn; Michiel Makkee; Ignacio Melián-Cabrera (173-181).
Display OmittedA strategy to enhance the thermal stability of C/SiO2 hybrids for the O2-based oxidative dehydrogenation of ethylbenzene to styrene (ST) by P addition is proposed. The preparation consists of the polymerization of furfuryl alcohol (FA) on a mesoporous precipitated SiO2. The polymerization is catalyzed by oxalic acid (OA) at 160 °C (FA:OA = 250). Phosphorous was added as H3PO4 after the polymerization and before the pyrolysis that was carried out at 700 °C and will extend the overall activation procedure. Estimation of the apparent activation energies reveals that P enhances the thermal stability under air oxidation, which is a good indication for the ODH tests. Catalytic tests show that the P/C/SiO2 hybrids are readily active, selective and indeed stable in the applied reactions conditions for 60 h time on stream. Coke build-up during the reaction attributed to the P-based acidity is substantial, leading to a reduction of the surface area and pore volume. The comparison with a conventional MWCNT evidences that the P/C/SiO2 hybrids are more active and selective at high temperatures (450–475 °C) while the difference becomes negligible at lower temperature. However, the comparison with reference P/SiO2 counterparts shows a very similar yield than the hybrids but more selective to ST. The benefit of the P/C/SiO2 hybrid is the lack of stabilization period, which is observed for the P/SiO2 to create an active coke overlayer. For long term operation, P/SiO2 appears to be a better choice in terms of selectivity, which is crucial for commercialization.
Keywords: Ethylbenzene; Styrene; Oxidative dehydrogenation; Carbon-based catalysts; Phosphorus; Thermal stability;

Support effect on structure and performance of Co and Ni catalysts for steam reforming of acetic acid by Saioa Goicoechea; Elka Kraleva; Sergey Sokolov; Matthias Schneider; Marga-Martina Pohl; Norbert Kockmann; Heike Ehrich (182-191).
Display OmittedSyngas production from acetic acid steam reforming was demonstrated. For this purpose Co or Ni with different metal loading supported on Al2O3 and ZnO were used as catalysts. The catalytic performance was studied in the 600–800 °C temperature range. The best ones were achieved at 800 °C over the following catalyst in the order of Ni/Al2O3  > Co/ZnO > Ni/ZnO, which provide high acetic acid conversions and high selectivities to the desired products, H2 and CO. As byproducts small amounts of CH4, acetone and ethylene were found, and their selectivity decreased with increasing reaction temperature. The internal morphology and structure of the catalyst was investigated by in-situ X-ray diffraction (XRD), transmission electron microscopy (TEM), and temperature programmed reduction (TPR) analysis. Morphological and structural modifications in the catalysts under reaction conditions, determined by the type of support and active metal, were closely related to the activity of the samples. High catalytic performance of Al2O3 supported samples is observed only over Ni-containing catalysts, due to the good dispersion of the active metal over the support, which promotes the formation of metallic Ni. The best performances of ZnO supported catalysts were achieved at high temperature, when formation of alloy structure was detected together with the complete reduction of the active metals.
Keywords: Acetic acid steam reforming; Syngas production; Ni(Co)/Al2O3 catalyst; Ni(Co)/ZnO catalyst; Alloy structure;

Formation of 1,3-butadiene from ethanol in a two-step process using modified zeolite-β catalysts by Alexander Klein; Kristina Keisers; Regina Palkovits (192-202).
Display OmittedCatalysts for the selective formation of 1,3-butadiene out of ethanol in a continuous two-stage gas-phase fixed bed reactor setup were developed. In the first stage, 20% acetaldehyde yield was aspired. This mixture was directly fed into the second stage facilitating enhanced selectivity to 1,3-butadiene. In the first stage, AgSiO2 and CuSiO2 were studied. Especially the copper based catalyst proved to be a selective and long-term stable system. In the second stage we tested different zeolite-β based catalyst systems which were modified in terms of their acidic and basic behaviour. We were able to reach 1,3-butadiene selectivities up to 72% at rather low temperatures of 573 K. Furthermore we could draw a direct correlation between the catalyst’s acidic and basic properties and their catalytic performance. The physical properties were analysed via X-ray diffraction, nitrogen physisorption, TGA–DSC and HRTEM. The chemical composition was determined by ICP-AES and SEM–EDX measurements. The investigation of the acidic and basic properties was realized by pyridine adsorption infrared spectroscopy and temperature programmed desorption with ammonia and carbon dioxide, respectively.
Keywords: Butadiene; Ethanol; Catalysis; Heterogeneous; Zeolite; Ion exchange; Acidity; Basicity;

Display OmittedPhysicochemical characterization of catalysts in surface and bulk manners is an area of vital importance in experimental heterogeneous catalysis. The knowledge of physicochemical properties such as overall surface area (internal and external), pore size distribution (distribution of micro-, meso-, and macro-pores) and pore volume, elemental composition, particle size and dispersion (and active metal surface area), coupled with the chemical surface reactivity, acid-base characteristics, and surface structures/bonding of the adsorbates, etc., enables one to decipher the important structure-property-performance relationships, or, the catalytic performance as a function of the physicochemical properties, as well as elucidate the reaction mechanisms and catalytic turnover cycles, to be able to design better (i.e., more efficient and chemo-selective) catalysts. The basic principles of characterization including physisorption, chemisorption, temperature-programmed techniques, X-ray techniques, analytical electron microscopy, and vibrational spectroscopies, are all drivers for development of a complete collage or suite of physiochemical properties, important for structure-property-performance relationships.A critical assessment first and then a comparative evaluation of the different methods available currently for the determination of metal particle size in supported metals is given. The determination of metal particle size is important to evaluate the so-called structure sensitivity of chemo-catalytic reactions. The methods that are currently available include substrate-specific selective chemisorption of suitable probe molecules, X-ray powder diffraction, analytical high-resolution transmission electron microscopy (in bright and dark field), small-angle X-ray scattering (SAXS and ASAXS) and X-ray absorption spectroscopy (XAS). Based on the state-of-the-art, selective chemisorption is perhaps the most sensitive technique, as all atoms are probed at the atomic level, independent of the crystallite size. Selective chemisorption also yields a surface-averaged particle size, which is more pertinent from the standpoint of catalytic science; X-ray diffraction and TEM measurements give volume- and particle number-averaged particle sizes. Some recent advances in the determination of particle sizes and in-situ evolutions of particle size distributions, structure of the metal-support interface, and the electronic properties of small metal clusters are also discussed.
Keywords: Particle size distribution; Selective chemisorption; X-ray powder diffraction; X-ray absorption spectroscopy; Small-angle X-ray scattering; Analytical electron microscopy;

Display OmittedUltrasound-assisted biodiesel production from waste cooking oil catalyzed by hydrotalcite (HT) catalyst prepared using combustion method was studied. Two important parameters in the HT synthesis i.e., calcination temperature (550–850 °C) and fuel type (saccharose, glucose and fructose) were particularly investigated. The dependence of HT’s characteristics on the synthesis parameters and correlations with their catalytic performance under ultrasound condition were successfully elucidated. The HT catalyst prepared using saccharose and calcined at 650 °C was the best catalyst to be used in the transesterification reaction. It showed high biodiesel yield (about 76.45%) in just 60 min in the presence of low ultrasound amplitude (∼11 kHz). The enhancement effect of ultrasound was successfully demonstrated. The reaction only needed short reaction time (about 1 h) to give a biodiesel yield of up to 76.45% compared to conventional stirring method that needed about 5 h to achieve the same yield.
Keywords: Ultrasound-assisted system; Biodiesel; Transesterification; Hydrotalcite; Combustion method;

The composition of Ni-Mo phases obtained by NiMoO x -SiO2 reduction and their catalytic properties in anisole hydrogenation by A.A. Smirnov; S.A. Khromova; D.Yu. Ermakov; O.A. Bulavchenko; A.A. Saraev; P.V. Aleksandrov; V.V. Kaichev; V.A. Yakovlev (224-234).
Display OmittedThe specific features of the formation of nickel- and molybdenum-containing phases during the reduction of the oxide precursor of the NiMoO x -SiO2 catalyst with hydrogen at three different temperatures (470, 570, and 750 °C) were studied. The reduction behavior was investigated and the reduction temperature of oxide forms was determined with the use of the methods of temperature-programmed reduction, X-ray diffraction analysis, and X-ray photoelectron spectroscopy. It was shown that, at a reduction temperature from 470 to 570 °C, one can observe the formation of NiMoO x particles with the NiO-type structure, Ni-Mo alloys of different composition, and MoO2, which pass into the metallic phases Mo, Ni3Mo, and Ni x Mo1-x at 750 °C. Nickel located at the surface is completely reduced to the metallic state in the temperature range of 300–750 °C, the Mo° content increases with the growing of treatment temperature and reaches 100% at 750 °C. Based on the data obtained, a reduction scheme for the catalytic system is proposed. The catalytic properties of the systems obtained are studied in the anisole hydrogenation reaction at a temperature of 300 °C and a hydrogen pressure of 6 MPa. The results of catalytic experiments showed that the 750-NiMo-SiO2 catalyst possesses the highest specific activity in the anisole hydrogenation, which is probably due to the complete reduction of nickel oxide forms and molybdenum to metallic forms, which are highly active in the hydrogenation of C―O bonds and aromatic rings. The highest selectivity in the formation of oxygen-free products can be attributed to the catalysts reduced at 470–570 °C and whose active component contains coordinatively unsaturated molybdenum atoms. The most stable during the thermal treatment in acetic acid is the 750-NiMo-SiO2 catalyst, which can be explained by the fact that it contains Ni-Mo alloys highly stable in the acid medium.
Keywords: Ni-Mo alloys; Hydrodeoxygenation; Hydrogenation; Anisole; NiMo-based catalysts;

Catalytic pyrolysis of cellulose using MCM-41 type catalysts by Andrés I. Casoni; María L. Nievas; Elizabeth L. Moyano; Mariana Álvarez; Alejandra Diez; Mariana Dennehy; María A. Volpe (235-240).
Display OmittedThe pyrolysis of microcrystalline cellulose in contact with MCM-41 and Fe, Al and Cu substituted samples was carried out at 400 °C in a fixed-bed glass reactor in order to obtain high bio-oils yields. The acid properties of the catalysts were determined by potentiometric titration with n-butylamine, while the redox properties were studied by TPR. BET surface area, pore volume and pore size were measured by means of N2 sorptometry. The effect of the different catalysts on the composition of the bio-oils was analyzed in the light of the characterization results. Mainly the concentration of levoglucosan (LG), levoglucosenone (LGO), 1,4:3,6-dianhydro-β-d-glucopyranose (DGP) and (1S,5R)-5-hydroxy-3,7-dioxabicyclo[3.2.1]octan-4-one (LAC) were measured. The presence of the solid catalysts increased the liquid formation and strongly modified the chemical composition of the bio-oils compared to the non-catalytic pyrolysis. All the catalysts decreased the production of LG and increased that of LGO, LAC and DPG. The mild acidity of the catalysts promoted dehydration reactions, while redox properties led to a higher production of isomerization products. A much higher LGO yield was obtained over Al-MCM-41 (53 wt% of cellulose is converted to LGO over this catalyst) than by non-catalytic pyrolysis of cellulose previously washed with phosphoric acid (7 wt% of washed cellulose is converted to LGO). In order to evaluate the reuse of the catalyst, the spent sample was submitted to calcination at 400 °C. The physicochemical properties were not modified after the calcination treatment and the pyrolysis employing the spent sample led to a similar bio-oil composition (though with a smaller yield) as in the case of the fresh catalyst. A second regeneration of the catalyst diminished the specific surface area and the surface acidity. Concomitantly a notable decrease of the yield of LGO was observed.
Keywords: Catalytic pyrolysis; Cellulose; MCM-41; Bio-oil; Levoglucosenone;

Rapid investigation of paraffin dehydrogenation catalyst by TPRn/SPI-TOF-MS technique for industrial application by Songbo He; Dong Chen; Huapeng Cui; Yulong Lai; Chenglin Sun; Haiyang Li; Ahmed S. Al-Fatesh; Ibrahim A. Aidid; Anis H. Fakeeha; K. Seshan (241-247).
Display OmittedDehydrogenation of long chain paraffins over commercial Pt-Sn-K-Mg/Al2O3 and Pt-Sn-Na-Co/Al2O3 catalysts were investigated using a temperature programmed reaction/single-photon ionization time-of-flight mass spectrometry (TPRn/SPI-TOF-MS) system under realistic reaction conditions using model compound C12 0 and in the industrial PACOL dehydrogenation plant using n-C10 0-C13 0 mixture. The catalysts were characterized by BET, mercury intrusion porosimetry, CO-chemisorption and NH3-TPD. Catalytic activity, selectivity to various components and stability were compared between TPRn/SPI-TOF-MS measurement and industrial plant run data to explore the reliability, predictability and application of TPRn/SPI-TOF-MS for rapid catalyst testing and screening. Characteristics of the catalysts, such as Pt dispersion and acidity, affected paraffin dehydrogenation conversion and mono-olefin selectivity. This was reflected in the catalyst performance data obtained on TPRn/SPI-TOF-MS system, which was in good agreement with the data from industrial runs. It is shown that use of TPRn/SPI-TOF-MS measurements allows to identify the reaction temperature range for maximum mono-olefin yield. Further it is possible to judge onset temperature for all the products and help identify operation temperature for industrial plant operation. Investigation of aromatics formation over the catalysts establishes the consecutive reaction pathways of long chain paraffin dehydrogenation over modified Pt-Sn/Al2O3 catalyst.
Keywords: Dehydrogenation; Temperature programmed reaction; Mass spectrometry; Time-of-flight; Heterogeneous catalysis;

Display OmittedCarbon nanotubes (CNTs)-supported Co-B amorphous alloy catalysts, with selective deposition of Co-B particles inside or outside of CNTs (labeled as Co-B-in/CNTs and Co-B-out/CNTs), were prepared based on the difference in the interface energies of organic and aqueous solutions with the CNTs surface. The catalysts were tested for the liquid-phase hydrogenation of m-chloronitrobenzene (m-CNB) to m-chloroaniline. Compared with Co-B-out/CNTs, Co-B-in/CNTs shows smaller, homogeneous size, and greatly improved thermal stability. The hydrogenation of m-CNB over Co-B-out/CNTs occurs on the outside of CNTs, while the hydrogenation of m-CNB over Co-B-in/CNTs occurs in the nanospace inside of CNTs. Co-B-in/CNTs exhibits a much higher activity than Co-B-out/CNTs.
Keywords: Co-B amorphous alloy; Supporting method; Carbon nanotubes; Hydrogenation; m-Chloronitrobenzene;

Display OmittedHere, we employed colloidal Pd and Pt nanoparticles synthesized by dendrimer templates as well as reverse microemulsions in the selective oxidation of styrene using tert-butyl hydroperoxide (TBHP) as an oxidant. We investigate their catalytic behavior and the feasibility as oxidation catalysts. High selectivity to styrene oxide, was achieved in the oxidation of styrene. The catalytic activities in terms of styrene conversion decreased in the order of dendrimer-templated Pd nanoparticles > thiol-capped Pd nanoparticles by reverse microemulsions > dendrimer-templated Pt nanoparticles > thiol-capped Pt nanoparticles by reverse microemulsions. This indicated that Pd-based catalysts were more efficient to catalyze the styrene oxidation reaction as compared to Pt-based catalysts. Furthermore, the dendrimer template synthetic method produced catalysts with higher activity as compared to those prepared by the reverse microemulsion template. The catalytic activities and selectivity profiles in various reaction conditions such as solvent type, styrene to TBHP ratio, type of catalysts, catalyst dosing, and temperature are discussed. The changes of average nanoparticle size after the reactions and the recyclability of Pd and Pt catalysts are examined. Overall results indicated that although higher catalytic activities were obtained with the use of dendrimer-templated nanoparticles, better recyclability as well as selectivity to styrene oxide was achieved with the use of thiol-capped Pd nanoparticles synthesized by reverse microemulsions.
Keywords: Pd nanoparticles; Pt nanoparticles; Dendrimer-templated; Reverse microemulsions; AOT/Isooctane/water; Hydroxyl terminated PAMAM dendrimer; Styrene oxidation;

Effect of the preparation method of supported Au nanoparticles in the liquid phase oxidation of glycerol by Nikolaos Dimitratos; Alberto Villa; Laura Prati; Ceri Hammond; Carine E. Chan-Thaw; James Cookson; Peter T. Bishop (267-275).
Display OmittedCatalytically-active gold nanoparticles that are stable in aqueous solution have been prepared by sodium borohydride reduction of the respective metal salts in the presence of the stabilising polymer PVA (polyvinylalcohol). By controlling the ratio of the polymer to the metal, nanoparticles with different particle size and size distribution were synthesised. By varying the concentration of the gold and PVA/Au wt/wt ratio, well-defined nanoparticles with mean diameters from 3 to 5 nm could be fabricated. In general increasing the concentration of Au precursor, bigger particles size were obtained. Furthermore decreasing the amount of PVA, bigger particles were obtained, with the exception of the catalysts synthesized in presence of a large amount of PVA (PVA/Au = 2) wt/wt. Probably, in presence of an excess of protective agent, the immobilization of the Au nanoparticles onto the support is more difficult, leading to partial aggregation and coalescence of Au. In addition, the studies on the effect of heat pre-treatment revealed a higher resistance to aggregation of Au nanoparticles supported on titania than on activated carbon. A selected series of the synthesised supported materials were studied in the liquid phase oxidation of glycerol with the purpose of correlating catalytic activity and selectivity with particle size and metal choice. We demonstrated that by both particles size and amount of protective agent strongly influence the activity and selectivity.
Keywords: Gold; Nanoparticles; Liquid phase oxidation; Heat treatment; Stabiliser effect;

Preparation and evaluation of Cu-Mn/Ca-Zr catalyst for methyl formate synthesis from syngas by Haijun Zhao; Minggui Lin; Kegong Fang; Juan Zhou; Yuhan Sun (276-283).
Display OmittedCu-Mn/Ca-Zr catalysts were prepared by mechanical mixing, sol-gel and impregnation methods. The phase structure, surface morphology and the chemical states of catalysts were characterized by XRD, TEM, SEM and XPS. The basic property and reducibility of catalysts were investigated by CO2-TPD and H2-TPR techniques. Several types of basic sites with different basicity could be observed on the surface of catalysts. The sample prepared by impregnation method has the lowest reducibility, and the sample prepared by sol-gel method shows the highest reducibility. The catalytic performance was evaluated for the direct synthesis of methyl formate from syngas in a slurry phase. The catalyst prepared by mechanical mixing method shows the highest CO conversion of 14.2% and methyl formate selectivity of 83.4% among these catalysts, which could be attributed to the large amounts of strong basic sites and low reducibility of the catalyst.
Keywords: Cu-Mn mixed oxides; CaO-ZrO2; Methyl formate; Mechanical mixing; Sol-gel; Impregnation;